1. Field of the Invention
This invention relates generally to devices utilized to separate a light beam into its spectral and/or polarization components and more specifically to a device which is utilized to separate a short-wavelength component of polarized light from other, orthogonally polarized components in a collinear laser beam.
2. Description of the Prior Art
Many devices are known to exist for the separation of two orthogonally polarized components of a single light beam. The family of Glan-type prisms, in which the wanted beam component is transmitted and the unwanted beam component is reflected, are such devices. However, Glan-type prisms are formed of calcite and are not suitable for the short-wavelength applications to which the instant invention is applied, due to the low transmission of calcite-based designs at such short wavelengths. A commercially offered "UV Glan-Taylor" device of reasonable dimensions has a transmittance of approximately 10% at 217 nm.
Another family of well known prism devices includes the Rochon and Wollaston types of prism separators, and variants thereof. Such devices are or can be composed of crystal quartz and are useful at short wavelengths. However, the wanted and unwanted components of the light beam are separated by only a small angle and therefore it is difficult to completely separate a wide beam in a short distance from the exit face of such devices. These non-Glan-type prior-art devices have the additional drawbacks that the wanted output beam is not necessarily collinear with the input beam, and the direction and/or position of the output beam may be a function of its wavelength
Dichroic reflectors, selective absorbers, and simple dispersing devices such as prisms and diffraction gratings, may be used for purely spectral separation. Simple prisms suffer all of the disadvantages of the aforementioned non-Glan-type prior-art devices. The other purely spectral devices are at best difficult to fabricate for use with the short wavelengths and high powers involved herein, and are not well suited for use in the important case where the wavelengths to be resolved vary widely. Gratings also suffer all of the disadvantages of simple prisms, except that they suffer the problem of overlapping multiple orders rather than that of small angular separation.